Wafer carriers or pods are utilized for holding, transporting, and storing substrates before, during and after processing. Such substrates are used in the fabrication of semiconductors such as integrated circuits and liquid crystal display panels. In their transformation into the end product, these delicate and highly valuable substrates are subjected to repeated processing, storage, and transportation. Such substrates must be protected from damage from particular contaminants, static discharges, physical damage from breakage, or contamination from vapors or gasses such as those outgassing from materials used in processing.
Such substrate containers are termed FOUPs, an acronym for front opening unified pods and FOSBs, an acronym for front opening shipping box. Industry standards specify that such substrate containers utilize kinematic couplings comprising three radially oriented grooves on the bottom of the container that interface with three rounded projections arranged in a triangle on the processing equipment. These kinematic couplings provide for the precise orientation of the wafer containers, thereby allowing for precise manipulation of the container and contents, for example robotic removal and insertion of the wafers. Such containers typically will have means for allowing robotic transfer of the containers with contents. Such means may include a robotic flange on the top of the wafer container as well as suitable rails or other features on the bottom of the container to allow the container to be suitably conveyed on conveyors with rollers or suitable carriages. It is apparent that sudden starts and stops, that is jarring of the wafer container with loaded wafers, can cause damage to the wafers. Thus, it is appropriate to provide suitable cushioning for the wafers during transport, including conveyance within a facility. The wafer restraints and exterior packaging conventionally provide such cushioning during transport from facility to facility. It is also desirable to have additional dampening and cushioning for the wafers when the containers are transported by way of conveyors that engage the bottom plate of the FOUP and/or FOSB's within a facility.
Such FOUP's and FOSB's utilize latching mechanisms in their doors with seals to create a hermetically sealed container. Such containers then need vents and/or purges to prevent deformation of the carrier or unintended leakages due to pressure differentials, for example, changes in barometric pressure. Utilizing such filters in various locations on the pods are known in the art and typically have an aperture in the shell with a suitable fixture and filter secured at the aperture.
Generally, it is considered desirable by the industry to minimize the number of openings leading into such containers. Prior art containers typically utilize molded-in openings in the shell portion for attachment of such filters or purging features.
In that the kinematic coupling must be precisely positioned with respect to wafer shells to allow for these precise interactions of processing equipment with the container and wafers, the positioning of the three grooves on the bottom of the wafer container with respect to the shelf location is absolutely critical. In that these wafer containers are conventionally molded of thermal plastics which may warp and distort during the molding process or subsequently, great care must be taken to provide this precise positioning. Known means for attaching the kinematic coupling features to the container portion include direct molding of the grooves in the shell, attachment of a separate plate with the grooves by way of screws, utilization of an interior super structure that includes the wafer shell and a lower plate that has the grooves and that is inserted within the shell portion. It would be desirable to utilize a separately molded plate attachable to the container that has adjustment capability and that is securely attached by more than the minimal near point attachment provided by screws. Such a separate plate can thus easily add additional features such as conveyor interface features, for example rails, coating means, and attachment means for other accessories by using different plate configurations or simply attaching the items to the plate. Also suitable means should ideally be provided for facilitating grounding of the wafer contact areas on the shell through the kinematic coupling to the kinematic coupling protrusions on the equipment or other receiving base upon which the wafer container is seated.